Normally for most TDS 500 series oscilloscopes, the DIP switch (S1001) typically all closed for normal operation. The only described use in the service manual is opening pin 6 and 7 to reveal the hidden composite test pattern screen for display adjustment.

However, I got a TDS 744 scope that boots very slow. Almost 5 mintues! To the extent that it’s unbearable. Initially I thought it’s just the non-A type booting slow. Nonetheless, I got a chance to open up another TDS 744A with boots much faster (in half a minute) with calibration seals on, and I noticed the pin 3 of S1001 is opened. Initially I thought it was out of place so I closed it again. Guess what? A slow 5 minute boot sequence!

I suspected opening pin 3 of S1001 puts the oscilloscope in the quick boot mode. I experimented with the pin 3 opened and manually initiating the full blown self-test (utility menu). Turns out I was correct! The full self-test is 5 minutes!

Since it was the settings from the calibration house, I looked up the TDS 744A/684A/784A service manual and noticed that the factory default is with pin 3 opened, while the old TDS 544A manual says pin 3 is closed. I suspect that the self-test for the new models 744/744A/684A/784A is unbearably long that the Tek decided to have it disabled for boot-up self-test.